Instructions:
- Prep Pan: Line an 8x8 inch metal baking pan completely with parchment paper, ensuring a slight overhang for easy removal later. Lightly grease the paper if desired.
- Roast Almonds: Spread almonds on a dry tray. Bake at 350°F (175°C) for 5-7 minutes until fragrant and lightly golden. Set aside to cool slightly.
- Combine Base: In a heavy-bottomed saucepan, combine butter, sugar, corn syrup, and water. Place over medium heat.
- Dissolve Sugar: Stir gently until the butter is melted and the sugar is fully dissolved. Stop stirring once the mixture begins to boil.
- Boil to Temperature: Insert a candy/sugar thermometer. Allow the mixture to boil undisturbed. Brush down any sugar crystals clinging to the sides of the pan using a wet pastry brush.
- Reach Hard Crack Stage: Continue boiling until the thermometer registers exactly 300°F (149°C). Remove immediately from heat.
- Incorporate Almonds: Working quickly and carefully, stir in the roasted almonds.
- Pour and Cool: Immediately pour the mixture into the prepared pan. Spread gently to an even layer using a heatproof spatula. Let it cool completely at room temperature for a minimum of 2 hours until hard.
- Melt Chocolate: Once the toffee is completely cool and hard, melt the dark chocolate using a double boiler or short bursts in the microwave.
- Spread and Season: Pour the melted chocolate evenly over the cooled toffee base. Immediately sprinkle generously with sea salt flakes before the chocolate sets.
- Set and Break: Allow the chocolate to set fully at room temperature. Once hard, lift the toffee out of the pan using the parchment overhang. Firmly break the slab into irregular pieces.